Control for recording platen in tensile testing machines



May 25, 1948. D. 'c. SCOTT 2,442,150

CONTROL FOR RECORDING PLATEN IN TENSILE TESTING MACHINES Filed July 16,1945 N 2 Sheet s-Sheet 1 INVEN OR fiavj'a co// ATTORNEYS y 1943- D. c.scoTT 2,442,150

CONTROL FOR RECORDING PLATEN IN TENSILE TESTING MACHINES Filed July 16,1945 2 Sheets-Sheet 2 ,zay.

a V I 6 ATTORNEYS Patented May 25, 1948 UNITED CONTROL FORRECORDINGPLATEN IN TENSILE TESTING MACHINES David C. Scott, Providence, R. 1.,assignor to Henry Rhode Island L. Scott Company, a corporation ofApplication July 16, 1945, Serial No. 605,390

7 Claims.

This invention relates to a testing machine of the inclined beam typeand more particularly to the control for the platen which is carried bythe beam and which records the behavior of the specimen being, tested.

In the use of a testing machine such as shown in my Patent No. 2,205,579dated June 2 5, 1940, where the beam swings through a relatively greatangular are, a slight variation may enter into the movement of theplaten relative to the beam by reason of the angular relation assumed bythe flexible element which is fixed to the base and extends up toandover a pulley on the beam and thence to the platen.

One of the objects of this invention is to pro-- vide an arrangement sothat the platen will move equal amounts relative to the beam for eachangular movement of the beam about its pivot.

Another object of the invention is to provide a simple arrangement sothat movement of the beam will unwrap aflexible element from a surfacewhich may be shaped to compensate for any irregularity and provide anarrangement so that the let-off of the flexible element will be in thedesired proportion to the angular movement of the beam.

With these and other objects in view, the invention consists of certainnovel features of con struction, as will be more fully describedandparticularly pointed out in the appended claims.

In the accompanying drawings:

Fig. 1 is an elevation of a testing machine equipped with the platenlet-off which is the sub- .iect of this invention;

Fig. 2 is a sectional view through the platen illustrating the flexibleelement attached to the platen with various other parts of the mechanismremoved;

Fig. 3 is a plan view of the cam surface diagrammatically showing itsarrangement relative to the pivot of the bea Fig. 4 is an edge view ofthe cam;

Fig. 5 is a fragmental view showing the uniform graph of the chart used;

Fig. 6 is a rear view of the testing machine shown in Fig. 1;

Fig. '1 is a sectional view through the platen with a modified form ofdrum;

Fig. 8 illustrates an eccentrically mounted drum of Fi '7;

Fig. 9 is an edge view thereof;

Fig. 10 is a fragmental view illustrating the error which may occur in amachine of the type illustrated in the above-mentioned patent.

In proceeding with this invention 1' have pro-i;

vided a cam. surface along which the flexible elementwhich controls theplaten extends. This surface is such that-"as the beam tilts theflexible element will be made available in. amounts to control thedescent of the platen in its guided path. The shape of the surface issuch that equal amounts of let-off are provided for equal amounts ofangular movement of the beam on its pivot.

With reference to the drawings 10 designates the base of the machinewith a standard ll projecting upwardly therefrom. A beam designatedgenerally I2 is pivoted on shaft l3 so that it may rock relative to thestandard H. The beam will be lowered through a fixed leg l4 providedthereon, which leg has rollers l5 and i6 engaging a yoke I! on the rackbar l8 which engages with a pinion in a gear box IS, the gears thereinbeing driven through a motor 20 and belt 2! and controlled by a lever2-2 having handle 23.

A clamp 24 is carried by the beam in order that a specimen 25 may befixed.- thereto. A clamp 26 engages the other end of the specimen and iscarried by a movable weight carriage 21 having wheels 28 to engage atrack 29 on the beam and be moved by gravity in response to the tiltingof the beam about the pivot 13. A bumper 30 mounted at 3| on the otherend of the beam is provided to catch and cushion the carriage should itmove suddenly after the break of a specimen.

Anti-friction roller 32, 33, 34, 35 are grooved to slidingly mount aplaten 36 having a clamp 31 thereon for the gripping of chart 38 whichis to be marked upon by an instrument 3-9 carried by rod 40 attached tothe carriage. This platen 36 will move by gravity at right angles to thebeam.

In order to control the movement of the platen I provide shaft 4|mounted on the roller frame in the back of the platen. A drum 42 isfixed on this shaft M and has a flexible element 43 fixed to the drumand coiled about it and extending to the lower edge of the platen as at44 (see Fig. l or Fig. 6). Thus, as the shaft turns the drum will windup or let off the flexible element 43. A drum 4'5 also secured to theshaft 41 and a flexible element 46 is attached to this drum and coiledabout it. flexible element extends along a slightly grooved surface 4''!which is in. the shape of a cam 48, the surface being eccentric to thepivot l3 about which the beam 12 swings. This cam is supported by an arm48' which is fixed with reference to the frame of the machine. As thebeam swings to the left in the position illustrated by Fig. 6, theflexible element '06 is unwrapped from the cam 48 thus permittinggravity to move the platen downwardly to wrap this element 46 about thedrum 45 as the platen descends. The amount the platen descends or moveswith reference to the beam will be controlled by the amount of let-offfrom this surface and accordingly I may control the amount of let-off bythe shape of the surface 48 so that the let-off will be proportional tothe angular swing of the beam about its pivot.

This cam surface 48 as shown in Fig. 3 is substantially on the arc of acircle but assuming that the pivot is at l3, see Fig. 3, I then move thecenter of this circle of radius 49 to a location 50 which in the case ofan are having a ten inch radius will be moved to the right an inch and ahalf and downwardly an inch and a half as one example of eccentricitywhich I have found to provide a correct relationship of cam surface tothe arcuate swing in a machine substantially of the proportion hereillustrated.

In Fig. 8 I have illustrated the drum on the shaft 4| as eccentricallyarranged which may be an optional means of controlling the platen in thecorrect amount. In this case a truly concentric surface for the cam 48with reference to the pivot l3 will be provided.

In Fig. 10 I have illustrated a diagrammatic view showing at angle 10the variation from a straight line which will occur during movement of abeam with a flexible element arranged as shown in Patent No. 2,205,579.The dot-dash line will be somewhat longer than a vertical from the pointH to the base 12, which would be the true distance desired if the amountof let-off was to be directly proportional to the angular relation ofthe beam.

I claim:

1. In atesting machine, a support, an inclinable beam mounted on saidsupport, a platen carried by said beam, said platen being movablerelative to said beam and laterally thereof by gravity whenunrestrained, a member fixed relative to said support, a rotatablemember mounted on said beam and movable therewith toward said fixedmember, means secured to said platen and operatively connected to saidrotatable member to restrain the movement of the platen, a flexibleelement extending between said members and secured thereto controllingthe rotation of said rotatable member, and eccentric means carried byone of said members and engaging said element and operable upon thetilting of the beam to control the length of said'element between saidmembers to cause movement of the platen relative to the beam directlyproportional to the angular are through which the beam moves.

2. A testing machine as set forth in claim 1 wherein said eccentricmeans comprises a surface from which said flexible element is unwrapped,the shape of said surface determining the relative movement of saidplaten and said surface being fixed.

3. In a testing machine, a support, an inclinable beam pivotally mountedon said support, a platen carried by said beam, said platen beingmovable relative to said beam and laterally thereof by gravity whenunrestrained, a member fixed relative to said support and having a camsurface thereon, a rotatable member mounted on. said beam and movabletherewith toward said fixed member, means secured to said platen andoperatively connected to said rotatable member to restrain the movementof the platen, and a flexible element extending between said members andover said cam surface for controlling the rotation of said rotatablemember whereby upon the tilting of the beam the flexible element isunwrapped from said cam surface to cause movement of the platen relativeto the beam directly proportional to the angular arc through which thebeam moves.

4. A testing machine, as set forth in claim 3, wherein said cam surfaceis substantially on the arc of a circle,

5. A testing machine as set forth in claim 4, wherein the center of thearc of the circle is positioned closely adjacent and spaced from thepivoted mounting of the beam.

6. In a testing machine, a support, an inclinable beam pivotally mountedon said support, a platen carried by said beam, said platen beingmovable relative to said beam and laterally thereof by gravity whenunrestrained, an arm extending generally toward said platen and fixedrelative to said support, a drum carried by said beam and movabletherewith toward said arm, means secured to said platen and operativelyconnected to said rotatable member to restrain the movement of theplaten, said arm having a curved surface extending in the generaldirection of the arc of movement of the beam, and a flexible elementextending between said drum and said arm and over said curved surfacefor controlling the rotation of said drum whereby upon the tilting ofthe beam the flexible element is unwrapped from said curved surface tocause movement of the platen relative to the beam directly proportionalto the angular are through which the beam moves.

7. In a testing machine having an inclinable beam movable on the arc ofa circle and a platen carried by said beam and movable relative theretolaterally thereof by gravity when unrestrained, means to cause movementof the platen relative to the beam directly proportional to the angularare through which the beam moves, said means including a support havinga surface fixed thereto and extending in the arc of a circle andpositioned to be eccentric with the arc of movement of said beam andflexible means engaging said eccentric surface and operatively connectedto said platen and through which the movement of the platen isrestrained, said flexible means being unwrapped from said surface as thebeam moves on an are about its pivot.

DAVID C. SCOTT.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,205,579 Scott June 25, 19402,286,651 Scott June 16, 1942

